package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @Description TODO
 * @Author Administrator
 * @Date 2019/12/26 21:06
 **/
public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1.获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //2.获取sql语句 select * from user where id=#{id} and name=#{name}
            //转换sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1,o);
        }

        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        List<Object> objects = new ArrayList<>();
        //6.封装结果集
        while(resultSet.next()){
            Object o =resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {

                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1.获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //2.获取sql语句 update users set id=#{id},username=#{username}
        BoundSql boundSql = getBoundSql(mappedStatement.getSql());
        //3.获取预处理statement
        PreparedStatement statement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            Field field = paramterTypeClass.getDeclaredField(content);
            field.setAccessible(true);
            Object o = field.get(params[0]);

            statement.setObject(i+1,o);
        }

        //5.执行sql
        int i = statement.executeUpdate();
        return i;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType!=null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作，1.将#{}使用？替代，2.解析#{}的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler handler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{","}",handler);
        String parseSql = genericTokenParser.parse(sql);
        ////#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = handler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }
}
